Stem cells are cells found in most, if not all, multi-cellular organisms. They are characterized by the ability to renew themselves through mitotic cell division and differentiating into diverse range of specialized cell types. The two broad types of mammalian stem cells are embryonic stem cells that are isolated from the inner cell mass of blastocytes, and adult stem cells that are found in adult tissues. In a developing embryo, stem cells can differentiate into all of the specialized embryonic tissues. In adult organisms, stem cells and progenitor cells act as a repair system for the body, replenishing specialized cells and also maintaining the normal turnover of regenerative organs such as blood, skin or intestinal tissues.
Mesenchymal stem cells are the formative pluripotential blast cells found inter alia in bone marrow, blood, dermis and periosteum that are capable of differentiating into any of the specific types of mesenchymal or connective tissues (i.e. the tissues of the body that support the specialized elements; particularly adipose, osseous, cartilaginous, elastic, and fibrous connective tissues) depending on various influences from bioactive factors, such as cytokines. Functionally speaking, stem cells have the ability to regenerate tissue over a lifetime. For example, the “gold standard” test for a bone marrow or hematopoietic stem cell (HSC) is the ability of the subject cell to rescue an individual who is without HSCs when the subject cell is transplanted to the individual. In this case, a stem cell must be able to produce new blood cells and immune cells over a long term, demonstrating potency. It should also be possible to isolate stem cells from the transplanted individual, which can themselves be transplanted into another individual without HSCs, demonstrating that the stem cell was able to self-renew.
Properties of stem cells can be illustrated in vitro using methods such as clonogenic assays where single cells are characterized by their ability to differentiate and self-renew. However, such methods are time consuming and cumbersome. Methods based on a distinct set of cell surface markers have been adopted. Markers that are associated with identifiable cell characteristics are valuable tools.
Medical researchers believe that stem cell therapy has the potential to dramatically change the treatment of human diseases. A number of adult stem cell therapies already exist, particularly bone marrow transplants for treating leukemia. In the future, researchers imagine being able to use technologies derived from stem cell research to treat a wide variety of diseases including cancer, Parkinson's disease, spinal cord injuries, amyotrophic lateral sclerosis, multiple sclerosis, and muscle damages, just to name a few. However, there still exists a great deal of scientific and technical uncertainties surrounding stem cell research.
Therefore, there still exists a need for research tools and methods that can be used to elucidate the disease mechanisms and advance the field of stem cell therapy and therapeutics.